The present invention relates generally to a disc brake incorporating a force transmission device.
Force transmission devices of disc brakes, particularly air actuated disc brakes, are mounted within a caliper of a brake and transmit an actuation force from an actuator to friction elements of the brake via tappets or pistons. Typically, the force transmission devices includes an adjuster mechanism that compensates for wear of the friction elements.
There are several drawbacks to known force transmission devices. For one, the high number of metal-to-metal sliding surfaces reduce efficiency. Additionally, the machining process used to provide a close fit between the tappet shafts and the housings is relatively expensive. The seals located near to the rear of the friction element may also be damaged in extreme high temperature applications. Furthermore, since the tappet heads are individual components, they must be securely attached to the tappet shafts, usually by a retaining ring or a circlip, increasing the number of parts. Finally, although cast iron backplates for friction elements are becoming more common, machining the backplate to ensure that the backplate is flat and the load from the force transmission device is adequately distributed over the backplate is expensive.